Threonine Needs of Finishing Broilers: Growth, Carcass, and Economic Responses

Abstract

Marginal dietary deficiencies of threonine, the third limiting amino acid in broilers, may result in economic losses from increased feed conversion and reduced breast meat accretion. It is important, therefore, to meet the minimum dietary threonine level needed in a broiler diet. Few studies, however, have addressed the threonine needs of finishing broilers. Those which have do not agree with current NRC standards. This study was conducted to determine the level of threonine needed for performance, the carcass traits of finishing broilers, and the economic importance of threonine in terms of profitability.A total of 4096 male commercial broilers received threonine-deficient diets containing corn, peanut meal, wheat middlings, poultry oil, and supplemental amino acids from 42 to 56 days of age. The experimental diets ranged from 0.45% to 0.81% total dietary threonine in 0.06% increments. This study included a corn-soybean-poultry meal control diet. Growth, feed conversion, and carcass responses of broilers fed the experimental diets supplement with surfeit threonine were equal to or better than responses obtained from broilers fed the control diet. A total dietary threonine level of 0.66% to 0.67% appears to be adequate to support good growth and carcass response in broilers from 42 to 56 days of age. Economic analysis indicated that the level of dietary threonine resulting in optimum profitability was near the level that resulted in optimum feed conversion and carcass composition.